The present invention relates to valves for controlling fluid flow, and more particularly to valves having a resilient diaphragm or similar member that is actuated by a solenoid to open and close a fluid passage.
Solenoid-operated valves are used extensively in many types of fluid distribution systems to control fluid flow. Such valves often employ a diaphragm or similar member made of a resilient material to achieve the desired sealing of one or more fluid passages in the valve when the valve is closed. The movement of the diaphragm between open and closed positions is controlled by the solenoid, which in turn receives a suitable electrical signal from any of a variety of control circuits. For example, the solenoid may be controlled by an output from a workstation that is executing a process control program. In one valve configuration, the diaphragm is pressed against a valve seat to close the valve. In this position the diaphragm sealingly covers one or more openings formed in the valve seat, thereby preventing fluid flow between passages that terminate at the openings. The diaphragm is drawn away from the valve seat to open the valve, and in this position uncovers the openings to allow fluid flow between the passages.
The fluids in some fluid control systems contain small particles in suspension that move through the system along with the fluids. The particles may be desirable constituents or undesirable by-products, such as sediment. In either case, the particles can deleteriously affect the fluid processing equipment. For example, within a valve of the type described above, the particles may be compressed between the diaphragm and the valve seat when the valve is closed. The particles reduce the effectiveness of the seal formed between the diaphragm and the valve seat, so that pressurized operation of the valve is compromised. Also, the particles induce wear (e.g. dents, scratches etc.) on the diaphragm, the valve seat, and other elements of the valve. This induced wear leads to a shortened lifetime and increased failure rate. Permanent damage can result causing leaks through the valve passageways and/or clogging of the valve during operation.
An additional shortcoming of many valves is relatively difficult maintenance. The configuration of some valves is such that the replacement of failure-prone parts entails the partial or complete disassembly of the valve, the availability of special tools or equipment, or other complicating considerations. These difficulties can substantially affect the cost of ownership over a valve's lifetime.
It is desirable to improve the ability of valves used with particle-bearing fluids to operate effectively during pressurized fluid delivery, and to reduce the wearing effect of fluid-borne particles on the elements of the valve, so that valve lifetime and failure rate are reduced. Additionally, it is desirable to improve the maintainability of valves in order to reduce total cost of ownership.